• Ancient Beringians

Who were the Ancient Beringians?

Ancient Beringians were a Native American group that formed a genetically distinct population between 21,000 and 11,500 years ago, and probably persisted in Alaska until about 6000 years ago. This population was discovered through genomic analyses on two infants discovered at the Upward Sun River site (USR) reported in Nature on Jan 3, 2018 (Figure 1). The discovery and analyses of these infants were reported in PNAS in 2014. The site is associated with the Denali complex, a widespread archaeological culture in Northwest North America.

The two infants were both female, and have been named Xach’itee’aanenh T’eede Gaay (sunrise girl-child) and Yełkaanenh T’eede Gaay (dawn twilight girl-child) by the local indigenous community. Genomic analysis of nuclear DNA from both individuals was conducted by Eske Willerslev’s team, led by J. Victor Moreno-Mayar, at the Centre for GeoGenetics at the University of Copenhagen’s Natural History Museum of Denmark. They were compared with ancient and modern populations and were found to be most closely related to Native Americans, but basal to all other branches. This indicates they were part of a previously unknown population of Native Americans.

Genomic modeling allowed for reconstruction of the population history of Ancient Beringians and other ancestral Native Americans (Figure 2). A single founding population of ancestral Native Americans began diverging from East Asians about 36,000+/-1500 years ago, with strong gene flow until ~25,000+/-1100 years ago. About 40% of ancestral Native American genes derived from another source, termed Ancient North Eurasians, around 25-20,000 years ago, indicating Native American ancestors were still in Asia (possibly near Lake Baikal) during this time. Our findings support a long-term genetic structure in ancestral Native Americans, consistent with the Beringian Standstill Model.

Around 22,000-18,100 years ago, ancestral Native Americans split into two groups, (1) Ancient Beringians, and (2) all other Native Americans. The latter population further split into two groups sometime between 17,500-14,600 years ago, into a North Native American (NNA) lineage (including Athabaskans and Algonkians) and a South Native American (SNA) lineage (including most other indigenous groups in North and South America) (Raghavan et al 2015). Gene flow between Ancient Beringians and SNA lasted until ~10,000 years ago, and with NNA until ~5000 years ago.

Figure 1. Reconstruction of Upward Sun River residential camp. The infants were buried within the structure in the foreground. 

Illustration by Eric S. Carlson in collaboration with Ben A. Potter.

Figure 2. A model of the formation of Native American ancestral populations 

(adapted from Moreno-Mayar, Potter, et al. 2018).

When did they migrate to North America?

The initial split of Ancient Beringians and other Native Americans (SNA+NNA) around 20,000 years ago likely took place in Asia (Scenario 1 in the Nature article) since (1) we have no secure evidence of American sites this old, (2) this period is characterized by very cold conditions (Last Glacial Maximum) where humans around Asia and Europe were contracting south (not expanding north), (3) previous genetic models of Native American demography indicate expansion only after 16,000-13,000 years ago (Llamas et al. 2016), and (4) we have a clear pattern of human expansion from southern Siberia to the Arctic and Beringia around 16-14,000  years ago, and the first widespread groups south of the ice sheets in the Americas after 13,500 years ago. Scenario 2 suggests the Ancient Beringian and SNA+NNA split occurred in East Beringia (Alaska). While this is genetically parsimonious (being in the same geographic region would have facilitated this period of gene flow between Ancient Beringians and other Native Americans), this scenario runs counter to the wide range of evidence summarized above. Scenario 1 is also consistent with the genetic data, as both groups could have been in the same or adjacent regions in northeast Asia, facilitating gene flow.

The NNA+SNA split around 17,500-14,600 years ago likely took place in an area separate from wherever the Ancient Beringians were located at this time, perhaps in northeast Asia (Scenario 1) or south/west of the ice sheets (Scenario 2). 

The Denali complex dates from around 12,500 to 6000 years ago, and suggests that the Ancient Beringians entered North America sometime between 16,000 and 12,500 years ago, and persisted in East Beringia and surrounding areas until around 6000 years ago.

The route(s) the NNA and SNA ancestors took remain unknown, but the Pacific coastal route was available by 16,000 years ago, while the interior Ice Free Corridor route was available by 15,000-14,000 years ago, and neither can be rejected at present. 

One plausible model is that at ~15,000 years ago, Ancient Beringians were in West Beringia (Asia) while NNA+SNA were in moving into East Beringia (Alaska). As deglaciation progressed (~14,500-13,500 years ago), one group (SNA) expanded through the Ice Free Corridor and radiated through North and later South America (Anzick [Clovis] is associated with SNA). A second group (NNA) expanded along the Northwest Coast, including Southeast Alaska (939, and possibly Shuka-Kaa is associated with NNA). These routes provide a plausible mechanism to separate the two lineages. By 14-13,000 years ago, Ancient Beringians expanded into Alaska. This model is consistent with gene flow between Ancient Beringians and SNA disrupted by the end of the Ice Age while gene flow between Ancient Beringians and NNA persisted through the Holocene.

What technology did they use?

A number of lines of evidence link the USR population with the Denali complex (or Paleoarctic tradition), a well-known archaeological culture represented by numerous sites and thousands of artifacts (Figure 3). Distinctive leaf-shaped stone points associated with USR are most consistent with Denali complex forms, and are dissimilar to the only other types in the region: Mesa, Sluiceway, and northern Fluted Point complexes. During the USR occupation, numerous Denali complex sites are found throughout interior Alaska, while other complexes are located in the Brooks Range or further away. A few km away, another site dating to the same period, Little Delta River #3, contains identical point types and microblade technology also distinctive to the Denali complex (Figure 4). Many other Denali sites contain one or both of these technologies, including recently excavated Delta River Overlook. Microblades are a distinctive Siberian tool, common in Northeast Asia between 20,000-6000 years ago, but it didn’t penetrate south beyond the Ice Sheets in North America, and may represent a connection to this Ancient Beringian population that remained in the far north. In this technology, small razor-blade like stone blades are inset into composite tools and used for various tasks, including as projectile points used to hunt mammoth and bison.

Tools at the USR site include formal bifacial and unifacial tools, like knives and scrapers, but also bifaces used as cores to generate thin flakes for use as other tools. Organic implements include decorated antler foreshafts used in hunting atlatl/dart weapons. Other organic tools like bone awls were also likely used, and while they haven’t been preserved at USR, they are found at other Denali sites, like Gerstle River, Mead and Broken Mammoth.

Figure 3. Geographic extent of the Denali complex / Paleoarctic tradition. Cloud derived from sites attributed to the Denali complex or American Paleoarctic tradition (yellow points) and other sites with wedge-shaped microblade cores (black points). Early Denali complex sites (pre-11 kya) are illustrated as red points.

Figure 4. Comparison of material culture at various Denali complex sites. Delta River Overlook contains 246 microblades and Little Delta River #3 contains about several dozen microblades. Artifacts illustrated by Eric S. Carlson.

How did they live in Beringia?

We have learned a lot about Denali complex (and now Ancient Beringian) lifeways through research at the USR site. Previous research indicates they hunted large game like bison and elk, but they also subsisted on small mammals (e.g. hare, ground squirrels) and birds. At Upward Sun River, a residential camp where women and children were present, we have evidence of large, medium, and small mammals, dominated by hare and ground squirrel, but also with the earliest evidence of salmon use in the Americas (Halffman et al. 2015; Choy et al. 2016). Evidence from USR, Gerstle River, and other sites indicates complex land use patterns, where logistically organized hunting parties specialized in megafauna like bison, processing them at spike camps (like Gerstle River), and bringing meat back to centrally located residential base camps like USR. Broad spectrum foraging of small game and fish occurred at these residential camps. This adaptive strategy was resilient and apparently persisted for over 6000 years in the Subarctic through many climatic and vegetation changes.

What happened to them?

The short answer is: we don’t know. We are limited by very few genetic samples of ancient North American populations, and we would need samples from peoples in the region to ascertain to what extent Ancient Beringian gene-flow occurred with neighboring peoples. It is possible that incoming Athabaskan ancestors (who are widespread throughout the region today) replaced or absorbed the Ancient Beringians inhabiting that area. Gene flow with Northern Native Americans occurred for thousands of years in the Holocene, indicating contact. Some of the Denali technologies persisted in the later Northern Archaic tradition, including microblades and burins, suggesting some level of continuity.

References

Moreno-Mayar VJ†, Potter BA†, Vinner L†, Steinrucken M, Rasmussen S, Terhorst J, Kamm JA, Albrechtsen A, Malaspinas A-S, Sikora M, Reuther JD, Irish JD, Malhi RS, Orlando L, Song YS, Nielsen R, Meltzer DJ, and E Willerslev (2018) Terminal Pleistocene Alaskan genome reveals first founding population of Native Americans. Nature. (doi:10.1038/nature25173)

Potter, Ben A., Joshua D. Reuther, Vance T. Holliday, Charles E. Holmes, Shane Miller, and Nicholas Schmuck. (2017) Early Colonization of Beringia and Northern North America: Chronology, Routes, and Adaptive Strategies. Quaternary International 444(b):36-55. (doi:10.1016/j.quaint.2017.02.034)

Choy, Kyungcheol†, Ben A. Potter†, Holly J. McKinney, Joshua D. Reuther, Shiway Wang, and Matthew J. Wooller†. (2016) Chemical profiling of ancient hearths reveals recurrent salmon use in Ice Age Beringia. Proceedings of the National Academy of Sciences. 113(35):9757-9762. Supporting Appendix, pp. 1-11. (doi:10.1073/pnas.1606219113)

Tackney, Justin, Ben A. Potter, Jennifer Raff, Michael Powers, Scott Watkins, Derek Warner, Joshua D. Reuther, Joel D. Irish, and Dennis H. O’Rourke (2015) Ancient DNA analyses from Terminal Pleistocene Burials in Eastern Beringia. Proceedings of the National Academy of Sciences 112(45):13833-13838. Supporting Appendix pp. 1-10. (doi:10.1073/pnas.1511903112)

Halffman, Carrin M†, Ben A. Potter†, Holly J. McKinney, Bruce P. Finney, A. T. Rodrigues, Dongya Y. Yang, and Brian M. Kemp (2015) Early Human Use of Salmon in North America at 11,500 years ago. Proceedings of the National Academy of Sciences 112(40):12344-12348. Supporting Appendix pp. 1-7. (doi:10.1073/pnas.1509747112)

Potter, Ben A., Joel D. Irish, Joshua D. Reuther, and Holly J. McKinney (2014) New Insights into Eastern Beringian Mortuary Behavior: A Terminal Pleistocene Double Infant Burial at Upward Sun River. Proceedings of the National Academy of Sciences 111(48):17060-17065. Supporting Appendix, pp. 1-24. (doi:10.1073/pnas.1413131111)

Potter, Ben A., Joel D. Irish, Joshua D. Reuther*, Carol Gelvin-Reymiller*, and Vance T. Holliday (2011) A Terminal Pleistocene Child Cremation and Residential Structure from Eastern Beringia. Science 331(6020):1058-1062. Supplementary Online Material: pp 1-14. (doi:10.1126/science.1201581)